Current responsive device



A ril 13, 1937. T. A. RICH 2,077,186

CURRENT RESPONSIVE DEVICE Filed Oct. 22. 1956 2 Sheets-Sheet 1 7 34flnventor'z Theodore A.Rich,

by M

Hi5 Attorney.

April 13, 1937. T. A. RICH CURRENT RESPONSIVE DEVICE Filed-Oct. 22, 19362 Sheets-Sheet 2 Inventor: "Theodore A. Rich,

His Attorney.

Patented Apr. 13, 1937 UNITED STATES CURRENT RESPONSIVE DEVICE TheodoreA. Rich,

Schenectady, N. Y., assignor to General Elect c Company, a corporationof New York Application October 22, 1936, Serial No. 107,002

6 Claims.

In carrying out my invention in its preferred form, I provide a fieldstructure with a pair of annular pole pieces and a shaft extendingthrough said pole pieces. A flat spiral of current-conducting materialattached at the inner end to the shaft and at the outer end to thestationary portion of the apparatus is mountedpn the shaft between thepole pieces and is provided with current connections. The arrangement issuch that radial force produced on the current-conducting spiral by thereaction between the current and the magnetic flux tends to wind orunwind the spiral, thus producing rotation of the shaft.

My invention may be understood more readily from the following detaileddescription when considered in connection with the accompanying drawingsand the features of my invention which a're believed to be novel andpatentable will be pointed out in the claims appended hereto. In thedrawings, Fig. 1 represents schematically in elevation one embodiment ofmy invention employing a single current-conducting spiral; Fig. 2

.is a plan view of the arrangement disclosed in Fig. 1; Fig. 3 is adiagram illustrating the principle of operation of the invention; Fig. 4is a plan view of a modified form of my invention in which one of thepole pieces is split to provide two air gaps and accommodate twocurrentconducting spirals; Fig. 5 is an elevation of the arrangement ofFig. 4; Fig. 6 is a fragmentary sectional view of the arrangement ofFig. 5 cut by a plane 6-6 passing throughthe axis of the armature of theinstrument; Fig. 7 shows a modification of the arrangement of Figs. 4,5, 5 and 6 illustrating the application of my invention to wattmeters orto alternating-current circuits; Fig. 8 is an elevation of a modifiedarrangement in which no magnet is required; and Fig. 9

is a view of a section cut through the apparatus of Fig. 8 by a plane9-9. Like reference characters are utilized throughout the drawings todesignate like parts.

Referring more in detail to Figs. 1 and 2, the stationary portion of theapparatus includes the field structure consisting of a permanent magvnetH with annular pole pieces l2 and 13, a scale I4, and bearings, notshown. The annular pole pieces l2 and 13 are substantially similar,substantially coaxial, and axially spaced to provide an air gap l5between them.

Th'e movable portion of the apparatus comprises a rotatable shaft IS,the current-conducting'spiral I! within the air gap l5, and a pointer l8carried by the shaft IE to cooperate with the scale 14. The shaft l6passes through the openings in the annular pole pieces I 2 and I3substantially coaxial therewith and the currentconducting spiral I! isattached at the inner end to the shaft l6 and at the outer end to aninsulated pin l9 attached to one of the pole pieces I3 or attached atsome other suitable position to the stationary portion of the apparatus.The

pin l9 forms one of the current-conducting terminals of the apparatusand the other terminal 20 may be connected to the shaft I6 in anysuitable manner, as e. g., by means of a substantially torsionlesscurrent-conducting spiral in the manner usual to current-responsiveinstruments of the dArsonval type.

If desired, suitable damping means may be provided, such asa dampingvane 2| of currentconducting material mounted on an arm 22 carried bythe shaft IS. The damping vane 2| is in close proximity to the innercylindrical surface 23 (Fig. 2) of the pole piece I 2. The eddy currentsinduced in the damping vane 2| provide an effective means for bringingthe movable element to a stop and preventing vibration thereof.

' It is evident that the magnet ll produces magnetic flux passingaxially across the air gap I 5 between the pole pieces I! and I3. Thecurrent flowing through the spiral ll passes perpendicularly to thelines of flux and, consequently, as shown in Fig. 3, the reactionbetween the flux and the current produces forces acting on the spiralligament ll perpendicular to the successive portions of the ligament l Iand also perpendicular to the shaft l6. Accordingly, each part of theligament I1 is subjected to a force acting in the plane of the ligamentI! through the center of the spiral formed by the ligament ll. Dependingupon the direction of current and the polarity of the pole pieces, theforces will be either outward or inward. In case the current directionis such that the forces are radially inward, as illustrated by thearrows in Fig. 3, the spiral ligament II will tend to wind up, thusrotating the shaft l8. In the case of a spiral wound as shown, the shaftwill be rotated in the clockwise direction. On the other hand, in thecase of reversal in the direction 01' current or reversal inpolarization oi. the magnet II, the spiral l1 will tend to unwind androtate the shaft It in the opposite direction. For reasons later tobe'explained, the former arrangement may give greater sensitivity.

It is apparent that the angle of deflection oi the shaft I 8 is notlimited to a fraction or 360 degrees but that a very long scaleinstrument may be produced. In fact, it. a suitable overhanging bearingsupport is provided which will not be struck by the pointer 18, theshaft i6 may be caused to rotate through a plurality of revolutions. Iidesired, a separate biasing spring orother suitable biasing means may beprovided for maintaining the pointer l8 in a predetermined zeroposition. However, it is apparent that such a biasing means isunnecessary in my construction for the reason that thecurrent-conducting spiral il itself serves as a biasing spring and, in

the case of center-zero instruments, serves to bias the pointer to aposition in the center of the scale. i

In connection with Figs. 1 and 2, it was mentioned that the currentconnection between the terminal 28 and the shaft l8 might take the formof a current-conducting spiral or hairspring. For the sake of obtainingincreased torque and for effective utilization of material, such asecond current-conducting spiral may be arranged in a second air gap, asshown in Figs. 4, 5 and 6. In the arrangement of Figs. 4, 5, and 6, thepole pieces are interleaved. One 01 the pole pieces is forked or splitinto two parts, 24 and 25, each of which is annular and is spacedaxially from an annular pole piece 26 in order to form a pair of airgaps 21 and 28. A pair of current-conducting spirals 28 and 30 areprovided in the air gaps 21 and 28, respectively, and each of thecurrent-conducting spirals 29 and 30 has its inner end attached to theshaft [6 or to a current conductor carried thereby and the outer ends ofthe current-conducting spirals 28 and 30 are electrically connected tobinding posts 3i and 32, respectively, serving as the terminals of theinstrument. The binding posts 3| and 32 are supported by the fieldstructure but insulated therefrom. The torque produced by the twospirals is in the same direction on IS.

Preferably, the current-conducting spiral ligaments H or 29 and 30 arecomposed of a material which combines the properties of high currentconductivity and high flexibility. I have 3 found certain copper alloysto be suitable for this purpose. For example, an alloy of 2.6% cobalt,97% copper, and 0.4% beryllium may be employed. The ligaments may be inthe form of thin strips in order to be sufliciently rigid to maintainthe proper position axially in the air gap and still offer very littleresistance to bending. The exact thickness will, of course, bedetermined by the current to be carried and the desired lull-scalereading of the instrument, which in turn determines the amount oi.control torque desired for calibration purposes.

\ In the arrangement of Figs. 4, 5,'and 6, the shaft I6 is mountedbetween cupped jewels carried in'the ends of jewel screws 33 and 34, re-

spectively. The jewel screws 33 and 34 are inounted in'suitablalijrackets 38 and 36, respec ively.

In the embodiments of my invention shown in with the armature so as toform an instrument having a modified relationship between current anddeflection. Such an instrument may also be employed for alternatingcurrents, in which case, the field structure is preferably partiallylaminated.

In Fig. '7, I have shown one manner of utilizing an electromagnet inconnection with my invention for providing a magnetic field. Thearrangement of Fig. 7 is connected for use as a wattmeter. It will beseen that the pole pieces [2 andl3 are attached to a yoke 31 upon whichis wound a field coil 38. The coil 38 is connected in series with theelectrical circuit 39 and the armature of the instrument is' connectedacross the circuit 39 through a resistor 40. The field coil 38accordingly serves as a current winding and the spiral ligaments .29 and38 serve as a potential winding of an instrument in which a torque isproduced varying with the product of the instantaneous values of currentand voltage. For use in alternating-current circuits, the yoke 31 ispreferably laminated and the pole pieces l2 and i3 may also be partiallylaminated.

It will be understood that my invention is not limited to the use of anyparticular form of damping mechanism. For example, in the arrangement ofFigs. 5 and 6, the damping element takes the form of a disk I carried bythe shaft IS in one of the air gaps and, as the shaft l6 rotates, itcauses the disk H to cut the magnetic center scale is desired, thearrangement will or-- dinarily be such that the flux produced by thepermanent magnet II or the solenoid winding 38 is relatively largecompared with the flux produced by the current flowing in thecurrentconducting spiral I'I. When such a directional effect is notdesired, this consideration need not be had but the arrangement willpreferably be such that the current-conducting spiral ll tends to windup rather than unwind is the current therein increases. It is evidentthat, in adjacent turns of the spiral ll, current is flowing in the samedirection and the reaction between such currents is such as to tend todraw the successive turns together. The resultant effect of the reactionbetween the current in successive turns of the spiral thus tends toclose or wind the spiral quite independently of any magnetic flux whichmay be produced by a field structure. Consequently, the torque producedby reaction between the currents in successive turns of the spiral maybe caused to aid the torque produced by the reaction between the currentin the spiral and the fiux produced by the field structure, and thesensitivity may be increased if the arrangement is such that thereaction between the current in the spiral and the fiux produced by thefield structure tends to wind up the spiral Il.

When it is desired to produce zero-center instruments having differentsensitivities in one direction or the other, the characteristic justdescribed may be made use of and the design may be such as to bringabout a relationship between field fiux and current which causes thereaction between the current in adjacent turns to suppress the scale forone direction of deflection and to expand the scale of the instrumentfor the other direction of deflection.

A modified arrangement is disclosed in Figs.

8 and 9 in which the reaction between the currents flowing in successiveturns of the spiral I1 is relied on for producing the turning moment ofthe armature of the instrument. Preferably, but not necessarily, a pairof currentconducting spirals 29 and 3ll is employed and is mounted inthe manner already described on a shaft l6 and terminals 3| and 32 andoccupies air gaps 26 and 21. The field structure, however, ispreferably-composed entirely of soft iron or some other suitable highlypermeable magnetic material and consists of a block of soft iron 43 withthe slots 26 and 21 cut therein to form air gaps. Suitable openings aredrilled therein to receive the shaft I6. The soft iron field structure43 serves to increase the sensitivity of the instrument by reducing themagnetic reluctance of the space surrounding the current-conductingspirals 29 and 30, respectively. It will be apparent that the instrumentillustrated in Figs. 8 and 9 is a universal instrument and may beemployed for measuring either alternating or direct currents. Thepointer I8 will tend to move in the direction corresponding to windingup the spirals 29 and 30, irrespective of the direction of current flow.

I have herein shown and particularly de-' scribed certain embodiments ofmy invention and certain methods of operation embraced therein for thepurpose of explaining its principle and showing its application, but itwill be obvious to those skilled in the art that many modifications andvariations are possible and I- aim, therefore,

to cover all such modifications and variations as fall within the scopeof my invention which is defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A current-responsive device comprising in combination, a fieldstructure having a pair of pole pieces, a relatively rotatable member,and a pair of current-conducting spirals, one of said pole pieces havingsubstantially parallel pole faces on either side thereof and the otherof said pole pieces being forked, the inner surfaces .of the forkedportion being substantially parallel to form pole faces, said first polepiece and said forked pole piece being interleaved with their pole facessubstantially parallel and spaced to form a pair of air gaps, saidcurrent-conducting spirals each being mounted in one of said air gapssubstantially parallel to said pole faces, the outer ends of saidcurrent-conducting spiral being mechanically connected to said fieldstructure and electrically insulated therefrom and the inner ends ofsaid current-conducting spirals being mechanically and electricallyconnected to ing in combination a field structure having a pair ofannular pole pieces substantially coaxial and axially spaced to form anair gap therebetween, a fiat current-conducting spiral within said airgap substantially perpendicular to the axis of said annular pole pieces,a rotatable shaft substantially coaxial with said pole pieces, and adamping loop carried by said shaft and linking one of said annular polepieces, said loop forming a closed electrical circuit, the inner end ofsaid current-conducting spiral being attached to said shaft and theouter end thereof being fixed in a stationary position.

3. A current-responsive instrument comprising in combination, a fieldstructure having a pair of pole pieces with substantially parallelconfronting pole faces spaced to form an air gap therebetween, a fiatcurrent-conducting spiral mounted in said air gap substantially parallelto said pole pieces, a rotatable member mounted with its axis ofrotation substantially perpendicular to said pole faces, and a. dampingmember of current-conducting material mounted on said rotatable memberand intersecting the path of lines of fiux between said pole faces, theinnerend of said current-conducting spiral being attached to saidrotatable member and the outer end being fixed in a stationary position.

4. A current-responsive wattmeter for an electrical circuit comprisingin combination, a stationary member including a magnetic field structureof magnetizable material having a pair of pole pieces with substantiallyparallel confronting pole faces spaced to form an air gap therebetweenand a current-conducting winding in inductive relation with saidmagnetizable field structure, a fiat current-conducting spiral mountedin said air gap substantially parallel to said pole faces, and arotatable member with an axis of rotation substantially perpendicular tosaid pole faces, the inner end of said current-conducting spiral beingattached to one of said members and the outer end being attached to theother of said relatively rotatable members, said field winding and saidcurrent-conducting spiral each being connected to the electrical circuitin which watts are to be measured, one being connected in responsiverelation to the current in said circuit to serve as a current windingand the other being connected in responsive relation to the voltageacross said circuit to serve as a potential winding.

5. A zero-center current-responsive device with unequal scaledistributions on either side of the zero points comprising incombination, a pair of relatively rotatable members and acurrent-conducting spiral, said spiral being connected at the inner endto one of said members and at the outer end to the other of saidmembers, one of said members including a magnet having a pair of polepieces with confronting substantially parallel pole faces spaced to forman air gap therebetween, the axis of relative rotation of said membersbeing substantially perpendicular to said pole faces, saidcurrent-conducting spiral being mounted in saidair gap, the strength ofthe magnet being such that appreciable winding torque is produced by thereaction between the current in the turns of the spiral relative tounwinding or winding torque which is produced by the reaction betweenthe current in the spiral and the fiux produced by the magnet.

6. A current-responsive device comprising in substantially parallelconironting surfaces spaced combination, a pair of relatively rotatablememto form an air gap therebetween, the axis of relabers and acurrent-conducting spiral, said spiral tive rotation of said membersbeing mbstantially being connected at the inner end to one or saidperpendicular to said confronting surfaces and 5 members and at theouter end to the other of said said current-conducting spiral occupyingsaid 5' members, one of said members comprising magair gap.

netizable material formed into a structure having THEODORE A. RICH.

